Two different assays, leukocyte adherence inhibition (LAI) and antibody dependent cellular cytotoxicity (ADCC) have been used to measure the immune responses of 69 melanoma patients, 116 patients with other tumours and 64 normal controls to a number of melanoma and control antigens. Using the LAI test, melanoma patients were significantly more reactive (43-69% positive) than normal controls (7-32% positive) to membrane extracts from 3 to 6 melanoma cell lines, and 4 to 6 extracts of melanoma biopsy specimens. However, the proportion of patients with other tumours reacting with 3 of these extracts was similar to melanoma patients. Melanoma patients were more reactive to the melanoma extract than to extracts of normal skin, normal muscle and 2 breast cancer cell lines. ADCC tests were used to detect anti-melanoma antibodies in patient sera. Preferential reactivity by melanoma patients was detected towards only 2 of the 6 melanoma cell lines tested--53% of 55 melanoma sera reactive to LiBr compared with 28% of 79 sera from patients with other tumours and 17% of 29 normal sera (P less than 0.05); 42% of 31 melanoma sera reactive to MM127 compared with 18% of 22 sera from other tumour patients (n.s.) and 5% of 20 normal sera (P less than 0.005). Melanoma patients tested against a number of melanoma cell lines by ADCC or antigen extracts by LAI generally reacted with one or more, but not all of them. Thus, incomplete cross-reactivity between different melanomas was observed. There was no correlation between results of the same patient in the 2 tests.